It's definitely true that people on salaries often do not know how to invest their money properly and end up spending instead. I know countless people dropping a large chunk of their salary on to things like car payments, which is a depreciating asset. They'll also spend extravagantly with little even going into savings. It is possible to grow a degree of financial freedom with responsible spending and learning a little bit about investing, but it will grow much faster than savings accounts. Lots of people I've found simply don't have the determination or persistence to pull it off.
It is a mistake when they already have a salary but do not set aside any of it to save, to pay an installment such as a car installment or others such as paying monthly bills is a normal thing, besides that some people who have a salary sometimes only have enough salary to meet their needs so there is no money at all that they save or invest.
Not everyone has to invest because everyone's income is different, some do have a salary that is enough to meet their needs and enough to save it, I myself do not invest but I force myself to save. Maybe someday I will invest when I understand it well.